BLM (Barrel length matters!)

[Barbourcreek]

Old school gun Barrel with over 4500 rounds fired
6.5 creedmoor
Factory 140 ELDM Hornady ammo


All right gentlemen so this morning I went and shot it with magneto speed and it came out to 18 inch -2470 and then it dropped to 2251 so I believe somethings wrong with the magneto speed I'm going to redo this with a LabRadar. I've also got Benchmark looking at donating a 30 caliber barrel 7 mm and a 65 so I can do it with a new barrel I'm gonna leave this up for the rest of the day and then I'm going to pull the video, just so you guys know that I'm doing the right thing and not just hiding the video if there was something wrong

 

[Calvin45]

I seem to have missed where it said what cartridge this was with

 

[Calvin45]

And the specifics of the load. I know Ive read the articles in Rifleshooter where they did this exact thing with .308, .300 win mag, and 7mm rem mag and if I recall correctly none of them lost this much velocity (like 500 fps) going from 26 to 18

 

[Darryle]

6.5 Creedmoor

 

[Calvin45]

6.5 Creedmoor

Thanks. That's nuts. Tho I do understand that once you get under 20 inches velocity reeeealllly starts dropping in a non linear way.

Still…it's pretty wild that the 7mm rem
Mag only lost about 250 fps average going from 28 to 20 inches and the delightfully efficient .308 Winchester, with 4 different loads, never lost even 300 fps going from 28 down to 16.5 inches!!!!

Going from 24 to 16 in a 300 Winnie only lost about 300.

That's actually so surprising.

 

[Mike D Texas]

Something seems off on that 18" velocity.

 

[Barbourcreek]

I seem to have missed where it said what cartridge this was with

6.5 creedmoor
Factory 140 ELDM Hornady ammo

 

[Calvin45]

Something seems off on that 18" velocity.

Agreed. If you Google the rifleshooter article where they chop a 300 win mag down one inch at a time all the way to 16 inches….the .300 win mag didn't lose velocity nearly that bad going from 22 to 18. It's a more "overbore" cartridge and a much greater total powder volume too (relevant as ridiculously overbore 22 caliber rifles still do okay with ordinary sporter length pipes…something like a .300 RUM it shows up more)

I can't get my head around how on earth a 6.5 creed would suffer from short barrel ballistic impairment worse than a .300 Winnie

 

[Barbourcreek]

And the specifics of the load. I know Ive read the articles in Rifleshooter where they did this exact thing with .308, .300 win mag, and 7mm rem mag and if I recall correctly none of them lost this much velocity (like 500 fps) going from 26 to 18

6.5 creedmoor
Factory 140 ELDM Hornady ammo

 

[Calvin45]

Though it is worth noting…maybe the factory ammo is loaded with one of these new(ish) generation progressive burn rate double base powders. That could change things. SUPERFORMANCE, LEVEREVOLUTION, rl17 and 26, the Winchester staBall series….they play by some truly different rules. The burn rate evolves and gets notably faster throughout the barrel…if the bullet leaves saif barrel before the burn rate on a progressive burn powder has reached its peak that'd be WAY more pronounced and erratic than a basic single base static burn rate powder, at least that makes sense to me. I could be dead wrong.

But I have worked a fair bit with SUPERFORMANCE powder by hodgdon and, well, let's just say it does weird things.

 

[dogz]

Something seems off on that 18" velocity.

Correctumundo....something changed en route.

I can't imagine this would be duplicatable, but it'd be fun to try. That 18" tube should well be in the 2551 range

 

[Barbourcreek]

I thought it was a bit much, I will give it a run again on the magneto speed I still have the barrel, the barrel did have over 4500 rounds fired out of it, rifling could be worn pretty bad and lack of pressure out of the 18"

 

[Barbourcreek]

Correctumundo....something changed en route.

I can't imagine this would be duplicatable, but it'd be fun to try. That 18" tube should well be in the 2551 range

I thought it was a bit much, I will give it a run again on the magneto speed I still have the barrel, the barrel did have over 4500 rounds fired out of it, rifling could be worn pretty bad and lack of pressure out of the 18"

 

[Calvin45]

I thought it was a bit much, I will give it a run again on the magneto speed I still have the barrel, the barrel did have over 4500 rounds fired out of it, rifling could be worn pretty bad and lack of pressure out of the 18"

That's an interesting thought too. Never had it myself but I guess it does make sense, at least to my insensible head , that a very worn barrel would tighten up moving from chamber to muzzle. One could think of it as a "gain squeeze" haha (marketing idea…it's not an old worn out barrel it's a special, premium "gain choked" barrel that realizes benefits from length!!!! )